29 research outputs found
Performance Analysis of OFDM with Peak Cancellation Under EVM and ACLR Restrictions
This paper presents performance analysis of an adaptive peak cancellation
method to reduce the high peak-toaverage power ratio (PAPR) for OFDM systems,
while keeping the out-of-band (OoB) power leakage as well as an in-band
distortion power below the pre-determined level. In this work, the increase of
adjacent leakage power ratio (ACLR) and error vector magnitude (EVM) are
estimated recursively using the detected peak amplitude. We present analytical
framework for OFDM-based systems with theoretical bit error rate (BER)
representations and detection of optimum peak threshold based on predefined EVM
and ACLR requirements. Moreover, the optimum peak detection threshold is
selected based on the oretical design to maintain the predefined distortion
level. Thus, their degradations are automatically restricted below the
pre-defined levels which correspond to target OoB radiation. We also discuss
the practical design of peak-cancellation (PC) signal with target OoB radiation
and in-band distortion through optimizing the windowing size of the PC signal.
Numerical results show the improvements with respect to both achievable bit
error rate (BER) and PAPR with the PC method in eigen-beam space division
multiplexing (E-SDM) systems under restriction of OoB power radiation. It can
also be seen that the theoretical BER shows good agreements with simulation
results
Beamforming Analysis and Design for Wideband THz Reconfigurable Intelligent Surface Communications
Reconfigurable intelligent surface (RIS)-aided terahertz (THz) communications
have been regarded as a promising candidate for future 6G networks because of
its ultra-wide bandwidth and ultra-low power consumption. However, there exists
the beam split problem, especially when the base station (BS) or RIS owns the
large-scale antennas, which may lead to serious array gain loss. Therefore, in
this paper, we investigate the beam split and beamforming design problems in
the THz RIS communications. Specifically, we first analyze the beam split
effect caused by different RIS sizes, shapes and deployments. On this basis, we
apply the fully connected time delayer phase shifter hybrid beamforming
architecture at the BS and deploy distributed RISs to cooperatively mitigate
the beam split effect. We aim to maximize the achievable sum rate by jointly
optimizing the hybrid analog/digital beamforming, time delays at the BS and
reflection coefficients at the RISs. To solve the formulated problem, we first
design the analog beamforming and time delays based on different RISs physical
directions, and then it is transformed into an optimization problem by jointly
optimizing the digital beamforming and reflection coefficients. Next, we
propose an alternatively iterative optimization algorithm to deal with it.
Specifically, for given the reflection coefficients, we propose an iterative
algorithm based on the minimum mean square error technique to obtain the
digital beamforming. After, we apply LDR and MCQT methods to transform the
original problem to a QCQP, which can be solved by ADMM technique to obtain the
reflection coefficients. Finally, the digital beamforming and reflection
coefficients are obtained via repeating the above processes until convergence.
Simulation results verify that the proposed scheme can effectively alleviate
the beam split effect and improve the system capacity
JNK pathway plays a critical role for expansion of human colorectal cancer in the context of BRG1 suppression
Tumor stem cells (TSCs), capable of self-renewal and continuous production of progeny cells, could be potential therapeutic targets. We have recently reported that chromatin remodeling regulator Brg1 is required for maintenance of murine intestinal TSCs and stemness feature of human colorectal cancer (CRC) cells by inhibiting apoptosis. However, it is still unclear how BRG1 suppression changes the underlying intracellular mechanisms of human CRC cells. We found that Brg1 suppression resulted in upregulation of the JNK signaling pathway in human CRC cells and murine intestinal TSCs. Simultaneous suppression of BRG1 and the JNK pathway, either by pharmacological inhibition or silencing of c-JUN, resulted in even stronger inhibition of the expansion of human CRC cells compared to Brg1 suppression alone. Consistently, high c-JUN expression correlated with worse prognosis for survival in human CRC patients with low BRG1 expression. Therefore, the JNK pathway plays a critical role for expansion and stemness of human CRC cells in the context of BRG1 suppression, and thus a combined blockade of BRG1 and the JNK pathway could be a novel therapeutic approach against human CRC
Pancreatic RECK inactivation promotes cancer formation, epithelial-mesenchymal transition, and metastasis
膵癌悪性化の分子機構解明 --RECK発現の低下が膵癌の浸潤・転移を引き起こす--. 京都大学プレスリリース. 2023-09-19.RECK is downregulated in various human cancers; however, how RECK inactivation affects carcinogenesis remains unclear. We addressed this issue in a pancreatic ductal adenocarcinoma (PDAC) mouse model and found that pancreatic Reck deletion dramatically augmented the spontaneous development of PDAC with a mesenchymal phenotype, which was accompanied by increased liver metastases and decreased survival. Lineage tracing revealed that pancreatic Reck deletion induced epithelial-mesenchymal transition (EMT) in PDAC cells, giving rise to inflammatory cancer-associated fibroblast–like cells in mice. Splenic transplantation of Reck-null PDAC cells resulted in numerous liver metastases with a mesenchymal phenotype, whereas reexpression of RECK markedly reduced metastases and changed the PDAC tumor phenotype into an epithelial one. Consistently, low RECK expression correlated with low E-cadherin expression, poor differentiation, metastasis, and poor prognosis in human PDAC. RECK reexpression in the PDAC cells was found to downregulate MMP2 and MMP3, with a concomitant increase in E-cadherin and decrease in EMT-promoting transcription factors. An MMP inhibitor recapitulated the effects of RECK on the expression of E-cadherin and EMT-promoting transcription factors and invasive activity. These results establish the authenticity of RECK as a pancreatic tumor suppressor, provide insights into its underlying mechanisms, and support the idea that RECK could be an important therapeutic effector against human PDAC
OFDM PAPR Reduction via Time-Domain Scattered Sampling and Hybrid Batch Training of Synchronous Neural Networks
Peak-to-average power ratio (PAPR) reduction in multiplexed signals in orthogonal frequency division multiplexing (OFDM) systems has been a long-standing critical issue. Clipping and filtering (CF) techniques offer good performance in terms of PAPR reduction at the expense of a relatively high computational cost that is inherent in the repeated application of fast Fourier transform (FFT) operations. The ever-increasing demand for low-latency operation calls for the development of low-complexity novel solutions to the PAPR problem. To address this issue while providing an enhanced PAPR reduction performance, we propose a synchronous neural network (NN)-based solution to achieve PAPR reduction performance exceeding the limits of conventional CF schemes with lower computational complexity. The proposed scheme trains a neural network module using hybrid collections of samples from multiple OFDM symbols to arrive at a signal mapping with desirable characteristics. The benchmark NN-based approach provides a comparable performance to conventional CF. However, it can underfit or overfit due to its asynchronous nature which leads to increased out-of-band (OoB) radiations, and deteriorating bit error rate (BER) performance for high-order modulations. Simulations’ results demonstrate the effectiveness of the proposed scheme in terms of the achieved cubic metric (CM), BER, and OoB emissions